1. Field of the Invention
The present invention relates to a plug-in coupling for connecting two fluid ducts.
More specifically, the present invention relates to a plug-in coupling for connecting a first fluid duct to a second fluid duct, where the first fluid duct has at least one retaining rib. The plug-in coupling includes a sleeve, which has radial openings. A cylindrical locking device is axially guided for displacement within the sleeve. The locking device has axially extending and elastically flexible retaining arms with a hook formed at the free end of the arms for engaging behind the retaining rib of the first fluid duct when the first fluid duct is axially introduced into the locking device. The arms have at their free ends a radially outwardly inclined face, which, when the sleeve and the locking device are moved axially apart, presses against a front edge of one of the radial openings in the sleeve. Thus, the hook more firmly engages with the retaining rib when the locking device and sleeve move axially away from each other. The arms also have at their free ends a radially inwardly facing inclined face that contacts the retaining rib when the locking device and sleeve move axially away from each other. The locking device has a release arm disposed between each of the retaining arms. The release arm projects radially outwardly, in an axially displaceable manner, through one of the radial openings in the sleeve. At least one sealing ring is disposed between an inner shoulder of the sleeve and the locking device.
2. Discussion of the Related Art
A plug-in coupling is disclosed by German Reference DE 44 13 346 C1. All of the components of this plug-in coupling and of the first fluid duct, which is usually a pipe socket that is to be inserted into the coupling, have dimensional tolerances. Thus, when the first fluid duct is inserted into the plug-in coupling, the first fluid duct can be deflected laterally, to a relatively large extent, with respect to the plug-in coupling (e.g., as a result of vibration in a motor vehicle). This is especially true if the surfaces in contact have the maximum permissible dimensional tolerance deviation. These lateral deflections result in an increased load being placed on the sealing ring, and, in extreme cases, leakage. If the fluid ducts and coupling members are used for the conveyance of combustible fluids, such as, fuel (e.g., gasoline), oil or gases, the fluid duct and coupling members must also have the maximum level of electrical conducting capacity to prevent an electrostatic charge from causing a spark, which could cause a fire. If the members do not fit each other exactly, a relatively high transition resistance could occur, which hinders the shunting off of electrostatic charges across these members.